maleic acid

Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

n. A colorless crystalline acid, HO2CCH:CHCO2H, used in textile processing and as an oil and fat preservative.

from Wiktionary, Creative Commons Attribution/Share-Alike License

n. an unsaturated organic dicarboxylic acid, HOOCCH=CHCOOH, the geometric isomer of fumaric acid; it is found in unripe fruit, and is used industrially in the production of polyester resins

from the GNU version of the Collaborative International Dictionary of English

n. An unsaturated dicarboxylic acid (HO.CO.CH=CH.CO.OH) of cis conformation, having various uses in the manufacture of artificial resins, the dyeing and finishing of wool, silk, and cotton, and also combined with certain drugs to make salts more soluble than the basic forms. The corresponding isomer having trans conformation, is identical in chemical formula, is called fumaric acid.